It is often necessary in case of damaged intervertebral disks but also other spinal injuries to brace two or more adjacent vertebrae by spondylodesis (fusion of vertebral bodies). Pedicle screws, which carry proximally on their rear side a tulip or rod mount, are screwed for this purpose into the vertebral bodies. A cross rod connecting a pedicle screw each and tulips in a plurality of vertebrae is braced in the tulips by means of tightening screws.
Even though it is known in this connection that pedicle screws may be configured with a spherical head or with a partially spherical head and a pressing element may be provided between the rod and the pedicle screw head, with which the tulip head and the pedicle screw can be oriented with one another monoaxially or multiaxially relative to one another at an angle, pressure screws always act directly on the (cross) rod. Although curvatures of the spine (kyphosis—chest, lordosis—lumbar region) can be taken into consideration and adapted by correspondingly bent connecting rods, undesired stresses may develop in the prior-art devices, because the tightening screw tightening the rod in the tulip head always acts at right angles, i.e., flatly in the direction of its own symmetry axis against the rod and thus it also braces this in this manner in the tulip head.